Recent years have witnessed an unprecedented growth in services and applications housed in modern data centers, such as web-search, scientific computations, social networks, file storage and distributed files systems. Today's data centers may host hundreds of thousands of servers, interconnected via switches, routers and high-speed links, making the choice of networking architecture within the data center of premium importance, as it impacts the data center scalability, cost, fault-tolerance, agility and power consumption.
Significant research effort has been devoted over the last decade to design efficient data center networks. However, major concerns have recently been raised about the power consumption of data centers and its impact on global warming and on the electricity bill of data centers. The US Environmental Protection Agency (EPA) has reported that power usage of data centers in the US has doubled between 2000 and 2006 to nearly 61 billion kilowatt-hours, accounting for 1.5% of the US total electricity demand.
Given the steadily increasing number of servers and the exponentially growing traffic inside data centers, conventional data centers networking architectures suffer from performance limitations such as links oversubscription and inefficient load balancing.